package com.xzz.tree;

/**
 * @author: hhz
 * @create: 2021-12-22 15:36
 * 236. 二叉树的最近公共祖先
 **/
public class LowestCommonAncestor {
    static class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;
        TreeNode(int x) {
            val = x;
        }
    }

    public static void main(String[] args) {
        TreeNode node1 = new TreeNode(3);
        TreeNode node2 = new TreeNode(5);
        TreeNode node3 = new TreeNode(1);
        TreeNode node4 = new TreeNode(6);
        TreeNode node5 = new TreeNode(2);
        TreeNode node6 = new TreeNode(0);
        TreeNode node7 = new TreeNode(8);
        TreeNode node8 = new TreeNode(7);
        TreeNode node9 = new TreeNode(4);
        node1.left = node2;
        node1.right = node3;
        node2.left = node4;
        node2.right = node5;
        node3.left = node6;
        node3.right = node7;
        node5.left = node8;
        node5.left = node9;
        TreeNode treeNode = lowestCommonAncestor(node1, node2, node3);
        System.out.println(treeNode.val);
        TreeNode treeNode1 = lowestCommonAncestor(node1, node2, node9);
        System.out.println(treeNode1.val);
    }
    public static TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        if(root==null){
            return null;
        }
        if(root == p){
            return root;
        }
        if(root == q){
            return root;
        }
        TreeNode left = lowestCommonAncestor(root.left, p, q);
        TreeNode right = lowestCommonAncestor(root.right, p, q);
        if(left!=null && right !=null){
            return root;
        }
        if(left==null && right ==null){
            return null;
        }
        return left==null?right:left;
    }
}
